Oil-free lubrication centrifugal refrigerant compressor and lubrication method thereof

ABSTRACT

An oil-free lubrication centrifugal refrigerant compressor for compressing low-pressure refrigerant into high-pressure refrigerant, includes: a housing; a refrigerant pathway; a compression module; a radial bearing; a first conducting member, collecting troughs and a first exhaust member. Therein, the compression module has a rotating shaft, a compressing member and a driving member; the radial bearing is rotatably disposed around the rotating shaft; the first conducting member conducts lubricating refrigerant fluid to the outer surface of the radial bearing and the inner surface of the rotating shaft so as to provide appropriate lubrication to the radial bearing and the rotating shaft when the driving member drives the rotating shaft to rotate and activate the compressing member to compress low pressure refrigerant into high pressure refrigerant; and the first exhaust member exhausts the lubricating refrigerant fluid, thereby solving the problem of contamination caused by using oil lubricants for compressors as encountered in prior techniques.

BACKGROUND

1. Field of the Invention

The present invention relates generally to centrifugal refrigerant compressors and lubrication methods thereof, and more particularly, to an oil-free lubrication centrifugal refrigerant compressor and a lubrication method thereof capable of oil-free lubricating a rotating shaft of the compressor.

2. Description of Related Art

A pressure device such as a centrifugal compressor works on a fluid (such as a refrigerant, air or water) through a rotating impeller activated by a rotating shaft in combination with such as a snail-shaped channel while the fluid is drawn into the compressor so as to pressurize and transport the fluid. To improve the operating efficiency of the compressor, it is critical to provide appropriate lubrication and support force to the rotating shaft so as to ensure stable and high-speed rotation of the rotating shaft. Accordingly, various bearing designs are proposed.

U.S. Pat. No. 7,240,515 discloses a magnetic bearing compressor with a rotating shaft suspended therein by a magnetic force. As such, when the rotating shaft rotates, it can be kept at an appropriate position without any friction with the surrounding components. However, the output of the magnetic force sufficient to support the supporting shaft consumes a lot of electric power. The output of the magnetic force also requires a precise control system, which not only increases the fabrication cost of the compressor but also results in more electric power consumption. Therefore, such a magnetic bearing compressor does not meet the energy-saving trend and increases the burden on the user.

U.S. Pat. No. 6,176,092 discloses a rolling element bearing compressor, which provides support force to a rotating shaft through rolling elements and uses liquid refrigerant instead of conventional oil lubricants for lubrication between the rolling elements and the rotating shaft so as to prevent environmental contamination and refrigerant pollution and even low thermal efficiency of refrigerant caused by using conventional oil lubricants. U.S. Pat. No. 5,902,049 discloses a compliant hydrodynamic bearing which provides support force to a rotating shaft through a buffer layer filled between the rotating shaft and the outer wall and further uses the elasticity of the buffer layer to reduce the probability of damage of the rotating shaft. Although the use of the liquid refrigerant as a lubricant avoids environmental contamination caused by conventional oil lubricants, the viscosity of the liquid refrigerant is not sufficient to provide a lubricating effect as good as that of the conventional oil lubricants, thus resulting in undesired damage of the rolling elements and the rotating shaft and increasing the risk of failure of the rolling element bearing compressor. Further, although the buffer layer reduces the probability of damage of the rotating shaft, it increases the damping coefficient between the rotating shaft and outer tube. As such, the compliant hydrodynamic bearing cannot be applied to a high speed compressor and has little practical application.

Therefore, it is imperative to provide an oil-free lubrication centrifugal refrigerant compressor and a lubrication method thereof so as to eliminate the need of an oil lubricant for lubricating a rotating shaft and ensure stable and high-speed rotation of the rotating shaft without consuming additional electric power.

SUMMARY

Accordingly, the present invention provides an oil-free lubrication centrifugal refrigerant compressor for compressing low-pressure refrigerant into high-pressure refrigerant, which comprises: a housing; a refrigerant pathway communicating with the housing and having a first pathway for inlet of low-pressure refrigerant and a second pathway for outlet of high-pressure refrigerant; a compression module disposed inside the housing and having a rotating shaft, a compressing member, a driving member that are connected with the rotating shaft, and a fixed outer wall encloses the outside of the rotating shaft, wherein the driving member drives the rotating shaft to rotate so as to activate the compressing member to compress the lower-pressure refrigerant into the high-pressure refrigerant; a radial bearing positioned between the fixed outer wall and the rotating shaft and rotatably disposed around the rotating shaft, wherein micro-spaces exist between an inner surface of the radial bearing and a surface of the rotating shaft and between an outer surface of the radial bearing and the fixed outer wall, and the radial bearing being further formed with at least a through hole communicating the outer surface thereof with the surface of the rotating shaft; a first conducting member disposed inside the housing and communicated with the outer surface of the radial bearing through the fixed outer wall so as to conduct lubricating refrigerant fluid to the outer surface of the radial bearing and further to the inner surface of the rotating shaft through the through hole of the radial bearing, thereby providing lubrication between the radial bearing and the fixed outer wall and between the radial bearing and the rotating shaft during operation of the compression module; a plurality of collecting troughs disposed at two ends of the radial bearing, respectively, and communicated with the micro-spaces for collecting the lubricating refrigerant fluid conducted to the outer and inner surfaces of the radial bearing and the rotating shaft through the first conducting member; and a first exhaust member communicated with the collecting troughs for exhausting the lubricating refrigerant fluid from the collecting troughs.

In an embodiment, the compressor further comprises an axial bearing disposed between one end of the rotating shaft of the compression module and the fixed outer wall, wherein the first conducting member is further communicated to the surfaces of the axial bearing for conducting the lubricating refrigerant fluid to surfaces of the axial bearing so as to provide lubrication between the axial bearing and the rotating shaft and between the axial bearing and the fixed outer wall during operation of the compression module, and the collecting troughs are further disposed around a periphery of the axial bearing so as to collect the lubricating refrigerant fluid conducted to the surfaces of the axial bearing through the first conducting member.

The present invention further provides a lubrication method of an oil-free lubrication centrifugal refrigerant compressor for lubricating a rotating shaft of the compressor and a fixed outer wall enclosing the rotating shaft, which comprises the steps of: (1) rotatably disposing a radial bearing having at least one through hole around the rotating shaft between the fixed outer wall and the rotating shaft, wherein micro-spaces exist between an inner surface of the radial bearing and a surface of the rotating shaft and between an outer surface of the radial bearing and the fixed outer wall, and the through hole communicates the outer surface of the radial bearing with the surface of the rotating shaft; and (2) conducting lubricating refrigerant fluid to the outer surface of the radial bearing through the fixed outer wall and further to the inner surface of the rotating shaft through the through hole of the radial bearing, thereby providing lubrication between the radial bearing and the fixed outer wall and between the radial bearing and the rotating shaft during operation of the rotating shaft.

In an embodiment, step (1) further comprises disposing an axial bearing between one end of the rotating shaft and the fixed outer wall; and step (2) further comprises conducting the lubricating refrigerant fluid to surfaces of the axial bearing through the fixed outer wall so as to provide lubrication between the axial bearing and the rotating shaft and between the axial bearing and the fixed outer wall.

Therefore, the oil-free lubrication centrifugal refrigerant compressor of the present invention uses the radial bearing and the axial bearing to provide a radial load force and an axial load force, respectively. When the compression module operates, the first conducting member can conduct lubricating refrigerant fluid into the compressor so as to provide appropriate lubrication between the radial bearing and the fixed outer wall, between the radial bearing and the rotating shaft, between the axial bearing and the fixed outer wall, and between the axial bearing and the rotating shaft, thereby ensuring stable and high-speed rotation of the rotating shaft. In addition, the compressor of the present invention does not need to consume additional electric power, eliminates the need of an additional control system and oil lubricants, thus reducing the burden on the user and avoiding environment contamination and refrigerant pollution caused by using oil lubricants as in the prior art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing the structure of an oil-free lubrication centrifugal refrigerant compressor of the present invention;

FIG. 2A is a front view of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to an embodiment of the present invention;

FIG. 2B is a cross-sectional view of the radial bearing of FIG. 2A;

FIG. 3A is a front view of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to another embodiment of the present invention;

FIG. 3B is a cross-sectional view of the radial bearing of FIG. 3A;

FIG. 4A is a front view of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to another embodiment of the present invention;

FIG. 4B is a cross-sectional view of the radial bearing of FIG. 4A; and

FIG. 5 is a flow diagram showing a lubrication method of the oil-free lubrication centrifugal refrigerant compressor of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those in the art after reading this specification.

FIGS. 1 to 4B show the structure of an oil-free lubrication centrifugal refrigerant compressor of the present invention, wherein FIG. 1 is a view showing the structure of the oil-free lubrication centrifugal refrigerant compressor of the present invention; FIGS. 2A and 2B are a front view and a cross-sectional view, respectively, of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to an embodiment of the present invention; FIGS. 3A and 3B are a front view and a cross-sectional view, respectively, of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to another embodiment of the present invention; and FIGS. 4A and 4B are a front view and a cross-sectional view, respectively, of a radial bearing of the oil-free lubrication centrifugal refrigerant compressor according to another embodiment of the present invention.

Referring to FIGS. 1 to 4B, the oil-free lubrication centrifugal refrigerant compressor 1 comprises a housing 10, a refrigerant pathway 11, a compression module 12, radial bearings 13 a, 13 b, an axial bearing 14, first conducting members 15 a, 15 b, 15 c, collecting troughs 16 a, 16 b, 16 c, 16 d, 16 e, first exhaust members 17 a, 17 b, 17 c, 17 d, a second conducting member 18 and a second exhaust member 19.

Therein, the refrigerant pathway 11 communicates with the housing 10 and has a first pathway 110 for inlet of low-pressure refrigerant and a second pathway 111 for outlet of high-pressure refrigerant.

The compression module 12 is disposed inside the housing 10 and has a rotating shaft 120, a compressing member 121 and a driving member 122 that are connected with the rotating shaft 120. Further, a fixed outer wall (not shown) encloses the outside of the rotating shaft 120. In particular, the driving member 122 drives the rotating shaft 120 to rotate so as to activate the compressing member 121 to compress the above-described low-pressure refrigerant into high-pressure refrigerant.

In the present embodiment, the compressing member 121 is a two-stage impeller and disposed to one end of the rotating shaft 120, and the driving member 122 is a high-speed variable-frequency motor stator. The compressing member 121 also can be a one-stage impeller or multi-stage impeller disposed at two ends of the rotating shaft 120. Further, inlet guide vanes 112 can be disposed inside the refrigerant pathway 11 for guiding the low-pressure refrigerant flowing into the first pathway 110 to the compressing member 121, thereby improving the compressing efficiency. In addition, the compression module 12 can further comprise a labyrinth seal ring 123 disposed to one end of the rotating shaft 120 close to the compressing member 121 so as to avoid leakage of the high-pressure refrigerant.

Referring to FIGS. 2A and 2B, the radial bearing 13 a is such as a floating ring disposed between the above-described fixed outer wall and the rotating shaft 120 and disposed in a freely rotatable manner around the rotating shaft 120 (at two ends of the rotating shaft 120 as shown in FIG. 1). There exist micro-spaces between the radial bearing 13 a and the rotating shaft 120 and between the radial bearing 13 a and the fixed outer wall. The micro-spaces can be such as 0.03 mm to 1 mm, and preferably 0.06 mm. Further, the radial bearing 13 a being formed with at least a through hole 130 a communicating the outer surface thereof with the surface of the rotating shaft 120. But it should be noted that the number and position of the radial bearing is not limited to the present embodiment. In other words, one single radial bearing 13 a or a plurality of radial bearings (for example, the two radial bearings 13 a, 13 b of FIG. 1) can be disposed around the rotating shaft 120 according to various practical needs.

In other embodiments, the radial bearings 13 a, 13 b can have a stacked structure. In other words, one or more radial bearings with larger inner diameters can be disposed around each of the radial bearings 13 a, 13 b so as to form a staked structure. Further, referring to FIGS. 2A and 2B, through holes 130 a, 130 b are disposed in the middle regions of the radial bearings 13 a, 13 b, respectively. In other embodiments, as shown in FIGS. 3A to 4B, a plurality of through holes can be disposed in the radial bearing 13 a along an circumferential direction (direction A) of the rotating shaft 120 or along an axial direction (direction B) in parallel to the rotating shaft 120, and the through holes correspond in position to each other. For example, in FIG. 3A, four through holes 130 a 1, 130 a 3, 130 a 3, 130 a 4 are disposed in the radial bearing 13 a at equal intervals around the circumferential direction of the rotating shaft 120, wherein the through holes 130 a 1 and 130 a 3 are disposed along a vertical axis orthogonal to an axial direction of the radial bearing 13 a and correspond in position to each other, and the through holes 130 a 2 and 130 a 4 are disposed along a horizontal axis orthogonal to the axial direction of the radial bearing 13 a and correspond in position to each other. Alternatively, as shown in FIGS. 4A and 4B, a plurality of through holes is disposed along the circumferential direction of the rotating shaft 120 and along the axial direction in parallel to the rotating shaft 120, and the positions of the through holes correspond in position to each other. As shown in FIG. 4A, the through hole 130 a 1 corresponds in position to the through hole 130 a 3, and the through hole 130 a 2 corresponds in position to the through hole 130 a 4. As shown in FIG. 4B, two groups of through holes, 130 a 1, 130 a 2, 130 a 3, 130 a 4 and 130 b 1, 130 b 2, 130 b 3, 130 b 4 are disposed in the radial bearing 13 a along the axial direction B in parallel to the rotating shaft 120.

The axial bearing 14 is disposed between one end of the rotating shaft 120 and the fixed outer wall for providing an axial load to the rotating shaft 120. In the present embodiment, the axial bearing 14 has a disc shape and is fixed between one end of the rotating shaft 120 and the fixed outer wall and in a direction perpendicular to the axial direction of the rotating shaft 120, wherein said one end of the rotating shaft 120 is disposed to the central region of the disc-shaped axial bearing 14.

As shown in FIG. 1, the first conducting members 15 a, 15 b, 15 c are disposed inside the housing 10. The first conducting member 15 a can have a straight tubular body with one end thereof facing the surface of the radial bearing 13 a. The first conducting member 15 b can have a T-shaped tubular body facing both the surface of the radial bearing 13 b and one surface of the axial bearing 14. The first conducting member 15 c can have a straight tubular body with one end thereof facing the other surface of the axial bearing 14. The first conducting members 15 a, 15 b, 15 c conduct lubricating refrigerant fluid (such as gaseous refrigerant or liquid refrigerant) to the surfaces of the radial bearings 13 a, 13 b and the axial bearing 14, respectively. Further, the lubricating refrigerant fluid on the inner and outer surfaces of the radial bearings 13 a, 13 b can flow to the surface of the rotating shaft 120 through the through holes 130 a, 130 b, respectively.

In particular, a thin film of lubricating refrigerant fluid is formed between the radial bearings 13 a, 13 b and the fixed outer wall, between the radial bearings 13 a, 13 b and the rotating shaft 120, between the axial bearing 14 and the rotating shaft 120, and between the axial bearing 14 and the fixed outer wall, respectively, such that when the compression module 12 operates, the thin film of lubricating refrigerant fluid can provide appropriate lubrication to the radial bearings 13 a, 13 b, the axial bearing 14 and the fixed outer wall, thereby avoiding frictional losses of the rotating shaft 120 and the fixed outer wall. Preferably, the first conducting members 15 a, 15 b can be aligned with the through holes 130 a, 130 b so as to precisely conduct the lubricating refrigerant fluid to the surface of the rotating shaft 120. It should be noted that the shape, number and disposing mode of the first conducting members 15 a, 15 b, 15 c can be varied according to the practical need.

The collecting troughs 16 a, 16 b are disposed to two ends of the radial bearing 13 a, respectively, so as to collect the lubricating refrigerant fluid conducted to the surfaces of the radial bearing 13 a and the rotating shaft 120 through the first conducting member 15 a. The collecting troughs 16 c, 16 d are disposed to two ends of the radial bearing 13 b respectively, so as to collect the lubricating refrigerant fluid conducted to the surfaces of the radial bearing 13 b and the rotating shaft 120 through the first conducting member 15 b. The collecting trough 16 e is disposed to the periphery of the axial bearing 14 so as to collect the lubricating refrigerant fluid conducted to the surface of the axial bearing 14 through the first conducting members 15 b, 15 c.

In the present embodiment, as shown in FIG. 1, the collecting trough 16 a communicates with the first exhaust member 17 a, the collecting trough 16 b communicates with the first exhaust member 17 c, the collecting trough 16 c communicates with the collecting trough 16 e through the first exhaust member 17 d, and the collecting trough 16 d covers the central region of the axial bearing 14. Therefore, the lubricating refrigerant fluid in the collecting trough 16 a can be exhausted through the first exhaust member 17 a, the lubricating refrigerant fluid in the collecting trough 16 b can be exhausted through the first exhaust member 17 c, the lubricating refrigerant fluid in the collecting trough 16 c flows into the collecting trough 16 e through the first exhaust member 17 d so as to form again a thin film of lubricating refrigerant fluid on one surface of the axial bearing 14 and finally the lubricating refrigerant fluid is collected in the collecting trough 16 e and exhausted through the first conducting member 17 b in communication with the collecting trough 16 e. Therein, the lubricating refrigerant fluid collected in the collecting troughs 16 a, 16 b, 16 e is exhausted to an evaporator (not shown).

Further, the driving member 122 of the compression module 12 can be connected with the second conducting members 18 and the second exhaust member 19. As such, the lubricating refrigerant fluid can be conducted to the driving member 122 through the second conducting member 18 that has such as a tubular body and exhausted through the second exhaust member 19 that has such as a tubular body. Further, recesses 131 a, 132 a can be disposed on the surface at two ends of the radial bearing 13 a facing the fixed outer wall and covered by the collecting troughs 16 a, 16 b, respectively so as to improve the lubricating refrigerant collecting efficiency of the collecting troughs 16 a, 16 b. Similarly, recesses 131 b, 132 b can be disposed to the surface at two ends of the radial bearing 13 b facing the fixed outer wall and covered by the collecting troughs 16 c, 16 d, respectively. Alternatively, the used lubricating refrigerant fluid can be first stored in the recesses 131 b, 132 b and then collected in the collecting troughs 16 c, 16 d so as to prevent leakage of excessive refrigerant fluid.

In practice, the first conducting members 15 a, 15 b, 15 c and the second conducting member 18 are connected with the outlet of a condenser (not shown) disposed at an outside of the housing 10. The second pathway 111 is a high-pressure gaseous refrigerant pathway, which communicates with the inlet of the condenser. The first exhaust members 17 a, 17 b and the second exhaust member 19 can be connected with an evaporator (not shown) or an economizer (not shown) disposed at an outside the housing and recyclable low-pressure refrigerant is exhausted to the evaporator or economizer. The first conducting members 15 a, 15 b, 15 c can further be connected with a pressure storage device (not shown) for storing and pressurizing the lubricating refrigerant fluid. After startup of the oil-free lubrication centrifugal refrigerant compressor 1, the pressure storage device opens its outlet so as to allow the lubricating refrigerant fluid to actively flow to the first conducting members 15 a, 15 b, 15 c by pressure provided by the pressure storage device.

Therefore, after startup of the oil-free lubrication centrifugal refrigerant compressor 1 of the present invention, the lubricating refrigerant fluid stored in the pressure storage device is actively conducted to the first conducting members 15 a, 15 b, 15 c by pressure so as to provide appropriate lubrication between the rotating shaft 120 and the radial bearings 13 a, 13 b and between the rotating shaft 120 and the axial bearing 14, thereby preventing frictional losses of the rotating shaft 120 that otherwise occur when the lubricating refrigerant fluid cannot be timely conducted thereto. Then, the rotating shaft 120 is driven to rotate at a high speed by the driving member 122 so as to activate the compressing member 121 to draw low-pressure gaseous refrigerant through the first pathway 110 and compress it into high-pressure gaseous refrigerant and exhaust the high-pressure gaseous refrigerant through the second pathway 111. Subsequently, the condenser converts the high-pressure gaseous refrigerant into liquid refrigerant and conducts the liquid refrigerant to the first conducting members 15 a, 15 b, 15 c such that the liquid refrigerant can be re-used as a lubricating refrigerant fluid. Meanwhile, the liquid refrigerant is conducted to the second conducting member 18 such that the liquid refrigerant is used as a cooling fluid for cooling the driving member 122 so as to maintain the working temperature of the driving member 122 within an appropriate range. Thereafter, the first exhaust members 17 a, 17 b and the second exhaust member 19 exhaust the liquid refrigerant to the evaporator or economizer so as for the liquid refrigerant to be converted into gaseous refrigerant again, thereby completing a refrigerant cycle.

It should be noted that since the liquid refrigerant can flow through such as the through hole 130 a so as to form a thin film of refrigerant fluid between the radial bearing 13 a and the rotating shaft 120 for lubrication, when the rotating shaft 120 rotates at a high speed, the thin film of refrigerant fluid between the radial bearing 13 a and the rotating shaft 120 can bring the radial bearing 13 a to rotate at a speed lower than the rotating speed of the rotating shaft 120. Therefore, the radial bearing 13 a provides a radial load force to the rotating shaft 120. For example, when the rotating speed of the rotating shaft 120 is 10000 RPM, the rotating speed of the radial bearing 13 a is 3000 RPM. Further, two thin films of refrigerant fluid formed on the inner and outer sides of the radial bearing 13 a improves dynamic stability of the rotating shaft 120 and reduces the probability of damage of the rotating shaft 120 and the radial bearing 13 a.

FIG. 5 shows a lubrication method of the oil-free lubrication centrifugal refrigerant compressor of the present invention.

At step S51, a radial bearing having at least a through hole is rotatably disposed around the rotating shaft between the rotating shaft and the fixed outer wall, wherein micro-spaces exist between the inner surface of the radial bearing and the surface of the rotating shaft and between the outer surface of the radial bearing and the fixed outer wall, and the through hole communicates the outer surface of the radial bearing with the surface of the rotating shaft. Then, the process goes to step S52.

At step S52, lubricating refrigerant fluid is conducted through the fixed outer wall to the surface of the radial bearing and further to the surface of the rotating shaft through the through hole of the radial bearing so as to provide lubrication between the radial bearing and the fixed outer wall and between the radial bearing and the rotating shaft.

In the present embodiment, after step S52 is performed, a plurality of collecting troughs can be disposed at two ends of the radial bearing so as to collect the lubricating refrigerant fluid on the surfaces of the radial bearing and the rotating shaft. Further, the lubricating refrigerant fluid collected in the collecting troughs can be exhausted to such as an evaporator or an economizer.

In another embodiment, at step S51, an axial bearing can be disposed between one end of the rotating shaft and the fixed outer wall such that the lubricating refrigerant fluid at step S52 can be collectively conducted to the surface of the axial bearing, thus providing lubrication between the axial bearing and the rotating shaft and between the axial bearing and the fixed outer wall during operation of the rotating shaft.

Further, in the present embodiment, a plurality of collecting troughs can be disposed around a periphery of the axial bearing so as to collect the lubricating refrigerant fluid on the surface of the axial bearing. The collected lubricating refrigerant fluid can further be exhausted to the evaporator or economizer.

Furthermore, in the above-described two embodiments, before step S52, a pressure storage device can be provided to store and pressurize the lubricating refrigerant fluid so as to allow the lubricating refrigerant fluid to actively flow to the surfaces of the radial bearing, the rotating shaft and/or the axial bearing by pressure provided by the pressure storage device.

Therefore, the oil-free lubrication centrifugal refrigerant compressor of the present invention uses the radial bearing and the axial bearing to provide a radial load force and an axial load force, respectively. When the compression module operates, the first conducting member can conduct lubricating refrigerant fluid into the compressor so as to provide appropriate lubrication to the radial bearing, the rotating shaft and the axial bearing, thereby ensuring stable and high-speed rotation of the rotating shaft and reducing frictional losses between the rotating shaft and the outer wall and saving electric power consumption. Further, the compressor of the present invention eliminates the need of an additional control system and oil lubricants. As such, the present invention reduces the fabrication cost and use cost. The present invention also avoids low thermal efficiency of refrigerant and environment contamination caused by using oil lubricants as in the prior art.

The above-described descriptions of the detailed embodiments are only to illustrate the preferred implementation according to the present invention, and it is not to limit the scope of the present invention, Accordingly, all modifications and variations completed by those with ordinary skill in the art should fall within the scope of present invention defined by the appended claims. 

1. An oil-free lubrication centrifugal refrigerant compressor for compressing low-pressure refrigerant into high-pressure refrigerant, comprising: a housing; a refrigerant pathway communicating with the housing and having a first pathway for inlet of low-pressure refrigerant and a second pathway for outlet of high-pressure refrigerant; a compression module disposed inside the housing and having a rotating shaft, a compressing member, a driving member that are connected with the rotating shaft, and a fixed outer wall encloses an outside of the rotating shaft, wherein the driving member drives the rotating shaft to rotate so as to activate the compressing member to compress the lower-pressure refrigerant into the high-pressure refrigerant; a radial bearing positioned between the fixed outer wall and the rotating shaft and rotatably disposed around the rotating shaft, wherein micro-spaces exist between an inner surface of the radial bearing and a surface of the rotating shaft and between an outer surface of the radial bearing and the fixed outer wall, and the radial bearing being further formed with at least a through hole communicating the outer surface thereof with the surface of the rotating shaft; a first conducting member disposed inside the housing and communicated with the outer surface of the radial bearing through the fixed outer wall so as to conduct lubricating refrigerant fluid to the outer surface of the radial bearing and further to the inner surface of the rotating shaft through the through hole of the radial bearing, thereby providing lubrication between the radial bearing and the fixed outer wall and between the radial bearing and the rotating shaft during operation of the compression module; a plurality of collecting troughs disposed at two ends of the radial bearing, respectively, and communicated with the micro-spaces for collecting the lubricating refrigerant fluid conducted to the outer and inner surfaces of the radial bearing and the rotating shaft through the first conducting member; and a first exhaust member communicated with the collecting troughs for exhausting the lubricating refrigerant fluid from the collecting troughs.
 2. The compressor of claim 1, further comprising an axial bearing disposed between one end of the rotating shaft of the compression module and the fixed outer wall, wherein the first conducting member is further communicated to surfaces of the axial bearing for conducting the lubricating refrigerant fluid to surfaces of the axial bearing so as to provide lubrication between the axial bearing and the rotating shaft and between the axial bearing and the fixed outer wall during operation of the compression module, and the collecting troughs are further disposed around a periphery of the axial bearing so as to collect the lubricating refrigerant fluid conducted to the surfaces of the axial bearing through the first conducting member.
 3. The compressor of claim 1, wherein one end of the first conducting member is connected with a condenser disposed at an outside of the housing, and one end of the first exhaust member is connected with an evaporator or an economizer disposed at the outside of the housing.
 4. The compressor of claim 1, further comprising a second conducting member and a second exhaust member connected with the driving member of the compression module, wherein the second conducting member conducts cooling fluid to the driving member and the second exhaust member exhausts the cooling fluid from the driving member.
 5. The compressor of claim 4, wherein one end of the second conducting member is connected with a condenser disposed at an outside of the housing, and one end of the second exhaust member is connected with an evaporator or an economizer disposed at the outside of the housing.
 6. The compressor of claim 1, further comprising a pressure storage device connected with the first conducting member for storing and pressurizing the lubricating refrigerant fluid so as to allow the lubricating refrigerant fluid to actively flow to the first conducting member by pressure when the compression module starts to operate.
 7. The compressor of claim 1, wherein the compression module further comprises a labyrinth seal ring disposed around the rotating shaft close to the compressing member so as to prevent leakage of the high-pressure refrigerant.
 8. The compressor of claim 1, wherein the collecting troughs at the two ends of the radial bearing communicate with the micro-spaces of the inner and outer surfaces of the radial bearing, and the micro-spaces range form 0.03 mm to 0.1 mm.
 9. The compressor of claim 1, wherein two through holes corresponding in position to each other are disposed in the radial bearing along each of a vertical axis and a horizontal axis that are orthogonal to an axial direction of the radial bearing.
 10. The compressor of claim 1, wherein two groups of through holes corresponding to each other are disposed in the radial bearing along an axial direction in parallel with the rotating shaft.
 11. A lubrication method of an oil-free lubrication centrifugal refrigerant compressor for lubricating a rotating shaft of the compressor and a fixed outer wall enclosing the rotating shaft, comprising the steps of: (1) rotatably disposing a radial bearing having at least one through hole around the rotating shaft between the fixed outer wall and the rotating shaft, wherein micro-spaces exist between an inner surface of the radial bearing and a surface of the rotating shaft and between an outer surface of the radial bearing and the fixed outer wall, and the through hole communicates the outer surface of the radial bearing with the surface of the rotating shaft; and (2) conducting lubricating refrigerant fluid to the outer surface of the radial bearing through the fixed outer wall and further to the inner surface of the rotating shaft through the through hole of the radial bearing, thereby providing lubrication between the radial bearing and the fixed outer wall and between the radial bearing and the rotating shaft during operation of the rotating shaft.
 12. The method of claim 11, further comprising step (3) of disposing a plurality of collecting troughs to two ends of the radial bearing so as to collect the lubricating refrigerant fluid on the inner and outer surfaces of the radial bearing and the surface of the rotating shaft.
 13. The method of claim 12, further comprising step (4) of exhausting the lubricating refrigerant fluid from the collecting troughs.
 14. The method of claim 13, wherein step (4) further comprises exhausting the lubricating refrigerant fluid to an evaporator and/or an economizer.
 15. The method of claim 11, wherein step (2) further comprises: (2-1) providing a pressure storage device for storing and pressurizing the lubricating refrigerant fluid; and (2-2) delivering the lubricating refrigerant fluid to the surfaces of the radial bearing and the rotating shaft by pressure provided by the pressure storage device.
 16. The method of claim 11, wherein step (1) further comprises disposing an axial bearing between one end of the rotating shaft and the fixed outer wall; and step (2) further comprises conducting the lubricating refrigerant fluid to surfaces of the axial bearing through the fixed outer wall.
 17. The method of claim 16, further comprising step (3) of disposing a plurality of collecting troughs around a periphery of the axial bearing so as to collect the lubricating refrigerant fluid on the surfaces of the axial bearing.
 18. The method of claim 17, further comprising step (4) of exhausting the lubricating refrigerant fluid from the collecting troughs.
 19. The method of claim 16, wherein step (2) further comprises: (2-1) providing a pressure storage device for storing and pressurizing the lubricating refrigerant fluid; and (2-2) delivering the lubricating refrigerant fluid to the surfaces of the axial bearing by pressure provided by the pressure storage device.
 20. The method of claim 18, wherein step (4) further comprises exhausting the lubricating refrigerant fluid to an evaporator and/or an economizer. 